It makes mailto: links open in an online email service (webmail services).
Currently it supports AOL mail, Fastmail, Gmail, Hotmail/Outlook, Yahoo mail and Zoho mail by default. You can also set multiple different email services yourself.
You can also choose to add an option to the context menu, to send the address of the page with your chosen email service. Furthermore, you can exclude certain web pages from this extension.
For support, please ask here: https://github.com/Famlam/mailto-chromeextension/issues. If you like this extension, please donate (in the options page).